A driver circuit includes a first deglitcher circuit that delays a rising edge or a falling edge of an input signal according to a mode control signal and supplies a first output signal. A second deglitcher circuit receives the first output signal and delays either a rising edge or a falling edge of the first output signal by a second delay according to the mode control signal and supplies a second output signal. Logic gates combine the first and second output signals to supply gate control signals for output transistors to drive the driver circuit output. A sum of the first delay and the second delay determines the total deglitch time defining a pulse width of pulses that are suppressed by the driver circuit and the second delay determines a non-overlap time. The non-overlap time overlaps in time with the total deglitch time.
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1. An apparatus for providing a driver output signal comprising:
a first deglitcher circuit to delay a rising edge of a first input signal responsive to a first value of a mode control signal and to delay a falling edge of the first input signal responsive to a second value of the mode control signal, the first deglitcher circuit to supply a first output signal; and
a second deglitcher circuit coupled to receive the first output signal as a second input signal and to delay a rising edge of the second input signal according to the first value of the mode control signal and to delay a falling edge of the second input signal responsive to the second value of the mode control signal, the second deglitcher circuit to supply a second output signal, the second output signal being coupled to the first deglitcher circuit and the second deglitcher circuit as the mode control signal.
13. A method for providing a driver output signal, the method comprising:
delaying a rising edge of a first input signal in a first deglitcher circuit responsive to a first value of a mode control signal and delaying a falling edge of the first input signal in the first deglitcher circuit responsive to a second value of the mode control signal and supplying a first output signal from the first deglitcher circuit;
receiving the first output signal at a second deglitcher circuit as a second input signal;
delaying a rising edge of the second input signal in the second deglitcher circuit responsive to the first value of the mode control signal and delaying a falling edge of the second input signal in the second deglitcher circuit responsive to the second value of the mode control signal and supplying a second output signal from the second deglitcher circuit; and
supplying the second output signal as the mode control signal.
19. A driver circuit comprising:
a first deglitcher circuit to delay by a first delay a rising edge of a first input signal to the first deglitcher circuit responsive to a first value of a mode control signal and to delay a falling edge of the first input signal responsive to a second value of the mode control signal, and supply a first output signal, the first delay being based at least in part on a first rc circuit in the first deglitcher circuit; and
a second deglitcher circuit coupled to receive the first output signal as a second input signal and to delay a rising edge of the second input signal by a second delay responsive to the first value of the mode control signal and to delay a falling edge of the second input signal responsive to the second value of the mode control signal, the second delay based at least in part on a second rc circuit in the second deglitcher circuit, the second deglitcher circuit to supply a second output signal that is coupled to the first deglitcher circuit and the second deglitcher circuit as the mode control signal.
2. The apparatus as recited in
a first NAND gate coupled to receive the first output signal and the second output signal as input signals and supply a first gate control signal;
a NOR gate coupled to receive the first output signal and the second output signal as input signals and supply a second gate control signal;
a first output transistor coupled between a power supply node and a driver output node supplying the driver output signal and coupled to the first gate control signal; and
a second output transistor coupled between the driver output node and a ground node and coupled to the second gate control signal.
3. The apparatus as recited in
4. The apparatus as recited in
5. The apparatus as recited in
6. The apparatus as recited in
7. The apparatus as recited in
8. The apparatus as recited in
9. The apparatus as recited in
10. The apparatus as recited in
11. The apparatus as recited in
12. The apparatus as recited in
14. The method as recited in
logically combining the first output signal and the second output signal in a NAND gate and supplying a first gate control signal;
logically combining the first output signal and the second output signal in a NOR gate and supplying a second gate control signal;
controlling a first output transistor coupled between a power supply node and a driver output node supplying the driver output signal using the first gate control signal; and
controlling a second output transistor coupled between the driver output node and a ground node using the second gate control signal.
15. The method as recited in
receiving the first input signal at a first inverter circuit in the first deglitcher circuit;
delaying either the rising edge or the falling edge of the first input signal based on a first rc time constant of a first rc circuit and generating a first delayed internal signal in the first deglitcher circuit on a first internal node; and
supplying the first delayed internal signal to a first inverting circuit of the first deglitcher circuit and supplying a first inverting circuit output as the first output signal.
16. The method as recited in
supplying a gate of a third-transistor with the mode control signal;
supplying a gate of a fourth transistor with the first input signal,
coupling a first power supply node to the first internal node through the third and fourth transistors when the third and fourth transistors are on;
supplying a gate of a fifth transistor with the mode control signal;
supplying a gate of a sixth transistor with the first input signal; and
coupling the first internal node to a ground node through the fifth and sixth transistors when the fifth and sixth transistors are on.
17. The method as recited in
receiving the first output signal as the second input signal at a second inverter circuit in the second deglitcher circuit;
delaying either the rising edge or the falling edge of the second output signal according to a second rc time constant of a second rc circuit and generating a second delayed internal signal in the second deglitcher circuit on a second internal node; and
supplying the second delayed internal signal to a second inverting circuit of the second deglitcher circuit and supplying a second inverting circuit output as the second output signal.
18. The method as recited in
supplying a gate of a seventh transistor with the mode control signal;
supplying a gate of an eighth transistor with the first output signal;
coupling the first power supply node to the second internal node through the seventh and eighth transistors when the seventh and eighth transistors are turned on;
supplying a gate of a ninth transistor with the mode control signal;
supplying a gate of a tenth transistor with the first output signal; and
coupling the second internal node to ground through the ninth and tenth transistors when the ninth and tenth transistors are turned on.
20. The driver circuit as recited in
21. The driver circuit as recited in
a first logic gate to logically combine the first output signal and the second output signal and supply a first gate control signal;
a second logic gate coupled to logically combine the first output signal and the second output signal and supply a second gate control signal, the first output transistor being coupled between a power supply node and a driver output node and coupled to the first gate control signal; and
the second output transistor being coupled between the driver output node and ground and coupled to the second gate control signal.
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This application is a continuation of U.S. patent application Ser. No. 17/125,561, filed Dec. 17, 2020, issued as U.S. Pat. No. 11,258,432, entitled “Deglitcher With Integrated Non-Overlap Function,” naming Péter Onódy et al., as inventors, which application is incorporated herein by reference in its entirety.
This disclosure relates to output drivers and more specifically to the delay associated with deglitching and nonoverlap functions for the output driver.
It would be desirable to reduce driver delay but current signal propagation delay solutions come with cost. For example, reducing the deglitcher delay will result a faster driver, but will also allow some unwanted glitches to pass through the driver. Thus, it would be desirable to reduce driver delay without affecting performance.
Embodiments described herein reduce the total delay of a driver without performance loss, thus keeping the original deglitch time and ensuring non-overlap.
In one embodiment an apparatus includes a first deglitcher circuit that delays by a first delay either a rising edge of a first input signal or a falling edge of the first input signal according to a mode control signal and supplies a first output signal. A second deglitcher circuit receives the first output signal as a second input signal and delays by a second delay either a rising edge of the second input signal or a falling edge of the second input signal according to the mode control signal and supplies a second output signal. The second output signal is coupled to the first deglitcher circuit and the second deglitcher circuit as the mode control signal.
In another embodiment a method includes delaying by a first delay either a rising edge of a first input signal or a falling edge of the first input signal in a first deglitcher circuit according to a mode control signal and supplying a first output signal. The method further includes a second deglitcher circuit receiving the first output signal as a second input signal and delaying by a second delay either a rising edge of the second input signal or a falling edge of the second input signal according to the mode control signal and supplying a second output signal. The method further includes supplying the second output signal as the mode control signal.
In another embodiment a driver circuit includes a first deglitcher circuit that delays by a first delay, based at least in part on a first RC circuit, either a rising edge of a first input signal or a falling edge of the first input signal according to a mode control signal and supplies a first output signal. A second deglitcher circuit receives the first output signal as a second input signal and delays by a second delay, based at least in part on a second RC circuit, either a rising edge of the second input signal or a falling edge of the second input signal according to the mode control signal and supplies a second output signal. A combination of the first delay and the second delay determines a pulse width of pulses that are suppressed in the driver circuit and the second delay further determines a non-overlap time to ensure an output PMOS transistor and an output NMOS transistor are not on at the same time. The second output signal is coupled to the first deglitcher circuit and the second deglitcher circuit as the mode control signal.
The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings.
The use of the same reference symbols in different drawings indicates similar or identical items.
Embodiments described herein integrate the nonoverlap delay (tNOL) into the deglitcher delay (tDGL) to reduce the total driver delay by the nonoverlap delay. The approach described herein reduces the total delay of a driver, while keeping the driver performance unchanged.
As described above the non-overlap delay (tNOL) ensures a delay between turning off the actual output device (M1 or M2) and turning on the other one (M2 or M1), to avoid a direct path between the supply rails.
Referring to
Let's suppose “in” 509 is 1 (the capacitor 505 is discharged) and the mode is “1” resulting in MN1 and MN2 being ON and MP1 and MP2 being OFF. If “in” 509 goes from high to low, MN1 turns off and the capacitor 505 is slowly charged through the resistor 503. If “in” 509 goes back to “1” before the voltage of the capacitor reaches the Schmitt trigger threshold of inverter 507 the output 511 stays high and the capacitor is quickly discharged back through the series transistors MN1 and MN2 (and also through R) and therefore the capacitor is quickly fully discharged waiting for the next pulse. Thus, negative going pulses smaller than the RC time constant of the RC network formed by resistor 503 and capacitor 505 are suppressed when the input and mode are both “1”.
Deglitcher circuit 603 provides both the non-overlap delay through the time constant τ2 provided by the RC network R2 and C2 and additional deglitching capability. The delay between the dly1 and dly2 nodes is the core delay of the nonoverlap function. Assume the input 609 to deglitcher circuit 603 is ‘0” and the output 605 (the mode signal) is also “0”. In this case an input rising edge on input 609 has to pass through the RC network R2C2 and is delayed by the RC time constant τ2 while a falling edge can bypass the RC network and directly drive the node n2 through the path provided by the series connected MP3 and MP4 transistors. The operation is the same when the input and output are 1, just vice-versa. That is, an input falling edge passes through the RC network and is delayed while an input rising edge directly drives node n2 to ground through the series connected MN3 and MN4 transistors.
In addition, the deglitcher circuit 603 provides an additional glitch suppression. Assume the deglitcher circuit 601 suppresses glitches having a pulse width up to τ1 and assume for this example that τ1=τ2. That is, the RC networks R1C1 and R2C2 have equal component values. Assume the input 607 to deglitcher circuit 601 is ‘0” and the output 605 (the mode signal) is also “0”. Assume that deglitcher circuit 601 receives a rising edge pulse that lasts for (1.5×τ1). When the pulse returns to “0”, the mode signal has not yet changed. INV2 switches from 0 to 1 after τ1 but returns to 0 after (˜τ½). Thus, deglitcher circuit 601 has shortened the negative going pulse from (1.5×τ1) to (˜τ½). Thus, deglitcher circuit 603 sees a pulse that is (τ½) and suppresses the pulse since it is less than τ2. Thus, the deglitching times of deglitching circuits 601 and 603 add together to provide tDGL while the second half of tDGL also provides the nonoverlap function. Thus, the driver has the same deglitching and nonoverlap performance but with less delay due to the overlap shown in
Note that the same deglitching occurs if the input is 1 and the mode is 1 and negative going pulse occurs. Assume the input 607 to deglitcher circuit 601 is ‘1” and the output 605 (the mode signal) is also “1”. Assume that deglitcher circuit 601 receives a falling edge pulse that lasts for (1.5×τ1). When the pulse returns to “1”, the mode signal has not yet changed. INV2 switches from 1 to 0 after τ1 but returns to 1 after (˜τ½). Thus, deglitcher circuit 601 has shortened the negative going pulse from (1.5× τ1) to (˜τ½). Deglitcher circuit 603 sees a pulse that is (τ½) and suppresses the pulse since it is less than τ2. Due to normal limitations of circuits and their operation the RC time constants may not be perfectly matched. In addition, stray capacitance and resistance in the deglitching circuits contributes to the delay and the other components of deglitching circuits cause additional delay in the transmission of the signal. Nevertheless, the RC time constants are the dominant factor in determining the delays through the deglitching circuits.
While the RC networks can have the same time constants such that τ1=τ2, other embodiments use different delays through the deglitching circuit 601 and 603. In addition, in some embodiments the delays are programmable by using variable resistors and/or variable capacitors for R1C1 and R2C2 to set the RC time constants to a desired value for a particular application.
Thus, a deglitching circuit that shortens driver delay while maintaining performance has been described. The description of the invention set forth herein is illustrative, and is not intended to limit the scope of the invention as set forth in the following claims. Other variations and modifications of the embodiments disclosed herein, may be made based on the description set forth herein, without departing from the scope of the invention as set forth in the following claims.
Onódy, Péter, Horváth, András V.
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